As per my experience most of the time the values shows as undefined when it actually not set in store. some of the time i also experience when store component shows undefined eventhough data stored in stores. Most of the time it works fine with context reset option which actually refresh the context cached data from store and for some time you can say its because of how stores implemented (persistent store Vs not persistent store) and that probably you can validate via going to edit page of client context component page http://<host>:<port>/etc/clientcontext/default/content.html.